1. Field of the Invention
The present invention relates generally to connection of equipment used in subsea operations, such as equipment used in the subsea oil and gas industry, to shore-based stations, and is particularly concerned with a subsea electrical/optical connector unit for connection between a subsea optical cable and an electrical cable in an ethernet transmission system and method for subsea communications.
2. Related Art
Subsea communication systems generally employ electrical ethernet through electrical telecommunications twisted pair cable, or are purely optical fiber communication systems. Purely electrical systems have some limitations in the subsea environment. Standard electrical input/output interconnects and electrical cables can only step out to a distance of around 50 meters. This is because a 10/100 BaseT ethernet cable has a maximum transmission distance of 100 meters at standard atmospheric pressure, after which the signal begins to degrade to an unrecognizable state. A full fiberoptic communication system overcomes this problem, but requires the land-based operator to convert the electrical input/output signals to optical signals prior to connection to the optical transmission system, both onshore and offshore, adding to the expense of such systems.
There are many types of connectors for making electrical and fiber-optic cable connections in hostile or harsh environments, such as underwater or subsea electrical, optical and hybrid electrical and optical connectors which can be repeatedly mated and demated underwater at great ocean depths. The connectors may be electrical only, optical only, or may be hybrid electrical and optical connectors. These connectors typically consist of releasably mateable plug and receptacle units or connector parts, each attached to cables or other devices intended to be joined by the connectors to form completed circuits. Each connector unit contains one or more electrical and/or optical contacts or junctions for engagement with the junctions in the other unit when the two units are mated together. To completely isolate the contacts to be joined from the ambient environment, one or both parts of these connectors house the contacts in oil-filled, pressure-balanced chambers.
The contacts on one side of a subsea or wet mateable electrical connector are typically in the form of pins or probes, while the contacts or junctions on the other side are in the form of sockets for receiving the probes. Typically, the socket contacts are contained in a sealed chamber containing a dielectric fluid or other mobile substance, and the probes enter the chamber via one or more sealed openings which include seals which exclude seawater and/or contaminants from the contact chamber in the mated and unmated conditions. Such electrical connectors are generally known as pin-and-socket type connectors. One example of an electrical underwater pin and socket connector is described in U.S. Pat. No. 5,645,442 of Cairns and is sold by Teledyne ODI, Inc. of Daytona Beach, Fla. under the name Nautilus®.